Methods and systems for improving the energy efficiency of carbon dioxide capture

ABSTRACT

A system for carbon dioxide capture from a gas mixture comprises a lean solvent comprising 3-amino-1-propanol (AP), 2-dimethylamino-2-methyl-1-propanol (DMAMP), and water; an absorber containing at least a portion of the lean solvent, wherein the absorber is configured to receive the lean solvent and a gaseous stream comprising carbon dioxide, contact the lean solvent with the gaseous stream, and produce a rich solvent stream and a gaseous stream depleted in carbon dioxide; a stripper, wherein the stripper is configured to receive the rich solvent stream; a cross-exchanger fluidly coupled to a rich solvent outlet on the absorber and a rich solvent inlet on the stripper; a reboiler fluidly coupled to a lower portion of the stripper; and a condenser fluidly coupled to a vapor outlet of the stripper.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND

Carbon dioxide (CO₂) is a greenhouse gas that, as a byproduct ofcombustion and a wide variety of industrial processes, is subject toincreasing regulation. As a result, there is a significant interest inefficient methods for capture CO₂ from such gas mixtures. Such methodsare often designed to capture CO₂ at low pressure (for example, fromflue gas), and typically are energy intensive. In traditional processes,an aqueous chemical solvent (typically an aqueous solution of MEA, AMP,and/or piperazine) is utilized in an absorber to absorb CO₂ in the formof chemical complexes with the solvent species and water, generating arich solvent. A stripper is utilized to release CO₂ from the richsolvent through the application of heat, to produce a lean solvent. Insuch processes a cross exchanger is utilized to improve efficiency byexchanging heat from the lean solvent into the rich solvent. The netheat that is added to the process is referred to as the stripper duty orenergy consumption. This energy consumption not only represents aconsiderable expense, the production of the necessary heat (for example,steam production) can result in the generation of additional CO₂ and/orreduction of the output (for example, electricity) of the plant.

SUMMARY

In an embodiment, a solvent for capture of carbon dioxide from a gasmixture may comprise 3-amino-1-propanol (AP), in a concentration rangingfrom 5 wt % to 45 wt %; 2-dimethylamino-2-methyl-1-propanol (DMAMP),where a mass ratio of DMAMP to AP is between about 1:11 and 5:1; andwater.

In an embodiment, a method for capturing carbon dioxide from a gasmixture may comprise contacting a gaseous stream comprising carbondioxide with a lean solvent, wherein the lean solvent comprises AP,DMAMP, and water; absorbing at least a portion of the carbon dioxide inthe lean solvent to produce a rich solvent; transferring the richsolvent to a stripper, wherein the stripper comprises a reboiler;applying heat to the rich solvent using the reboiler; generating a vaporstream within the reboiler while incurring an energy consumption toregenerate the lean solvent, wherein the vapor stream comprises steamand at least a portion of the carbon dioxide from the rich solvent; andtransferring the vapor stream to a condenser.

In an embodiment, a system for carbon dioxide capture from a gas mixturemay comprise a lean solvent comprising AP, DMAMP, and water; an absorbercontaining at least a portion of the lean solvent, wherein the absorberis configured to receive the lean solvent and a gaseous streamcomprising carbon dioxide, contact the lean solvent with the gaseousstream, and produce a rich solvent stream and a gaseous stream depletedin carbon dioxide; a stripper, wherein the stripper is configured toreceive the rich solvent stream; a cross-exchanger fluidly coupled to arich solvent outlet on the absorber and a rich solvent inlet on thestripper; a reboiler fluidly coupled to a lower portion of the stripper,wherein the reboiler is configured to generate a vapor stream from therich solvent and pass the vapor stream back to the stripper; and acondenser fluidly coupled to a vapor outlet of the stripper.

These and other features will be more clearly understood from thefollowing detailed description taken in conjunction with theaccompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, referenceis now made to the following brief description, taken in connection withthe accompanying drawings and detailed description, wherein likereference numerals represent like parts.

FIG. 1 is a schematic illustration of an embodiment of a carbon dioxidecapture system according to an embodiment.

FIG. 2 illustrates the effect of the solvent composition on the totalenergy consumption according to an embodiment.

DETAILED DESCRIPTION

It should be understood at the outset that although illustrativeimplementations of one or more embodiments are illustrated below, thedisclosed systems and methods may be implemented using any number oftechniques, whether currently known or not yet in existence. Thedisclosure should in no way be limited to the illustrativeimplementations, drawings, and techniques illustrated below, but may bemodified within the scope of the appended claims along with their fullscope of equivalents.

The following brief definition of terms shall apply throughout theapplication:

The term “comprising” means including but not limited to, and should beinterpreted in the manner it is typically used in the patent context;

The phrases “in one embodiment,” “according to one embodiment,” and thelike generally mean that the particular feature, structure, orcharacteristic following the phrase may be included in at least oneembodiment of the present invention, and may be included in more thanone embodiment of the present invention (importantly, such phrases donot necessarily refer to the same embodiment);

If the specification describes something as “exemplary” or an “example,”it should be understood that refers to a non-exclusive example;

The terms “about” or “approximately” or the like, when used with anumber, may mean that specific number, or alternatively, a range inproximity to the specific number, as understood by persons of skill inthe art field; and

If the specification states a component or feature “may,” “can,”“could,” “should,” “would,” “preferably,” “possibly,” “typically,”“optionally,” “for example,” “often,” or “might” (or other suchlanguage) be included or have a characteristic, that particularcomponent or feature is not required to be included or to have thecharacteristic. Such component or feature may be optionally included insome embodiments, or it may be excluded.

Disclosed herein are apparatus, systems, and methods for the use of aspecific acid gas solvent to reduce the total energy consumption of anabsorption-stripping process utilized in the capture of carbon dioxide.In general, the solvent can include AP, DMAMP, and water. Surprisingly,the use of the specific solvent can reduce the overall energyconsumption of the system relative to the energy consumption associatedwith pure component solvents having only AP or DMAMP. Thus, the presentdisclosure provides an improved solvent that has reduced total energyconsumption for the absorption-stripping process.

In addition to the reduction in energy consumption, the use of thesolvent described herein can help to reduce the degradation of thesolvent over time. This may help to reduce the amount of makeup solventneeded in a system as well as reducing the need for solvent reclamationsystems.

Various objects, features, aspects and advantages of the inventivesubject matter will become more apparent from the following detaileddescription of preferred embodiments, along with the accompanyingdrawing figures in which like numerals represent like components. Thefollowing description includes information that may be useful inunderstanding the present invention. It is not an admission that any ofthe information provided herein is prior art or relevant to thepresently claimed invention, or that any publication specifically orimplicitly referenced is prior art.

In some embodiments, the numbers expressing quantities of ingredients,properties such as concentration, reaction conditions, and so forth,used to describe and claim certain embodiments of the invention are tobe understood as being modified in some instances by the term “about.”Accordingly, in some embodiments, the numerical parameters set forth inthe written description and attached claims are approximations that canvary depending upon the desired properties sought to be obtained by aparticular embodiment. In some embodiments, the numerical parametersshould be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques. Notwithstandingthat the numerical ranges and parameters setting forth the broad scopeof some embodiments of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspracticable. The numerical values presented in some embodiments of theinvention may contain certain errors necessarily resulting from thestandard deviation found in their respective testing measurements.

As used in the description herein and throughout the claims that follow,the meaning of “a,” “an,” and “the” includes plural references unlessthe context clearly dictates otherwise. Also, as used in the descriptionherein, the meaning of “in” includes “in” and “on” unless the contextclearly dictates otherwise.

The recitation of ranges of values herein is merely intended to serve asa shorthand method of referring individually to each separate valuefalling within the range. Unless otherwise indicated herein, eachindividual value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g. “such as”) provided with respectto certain embodiments herein is intended merely to better illuminatethe invention and does not pose a limitation on the scope of theinvention otherwise claimed. No language in the specification should beconstrued as indicating any non-claimed element essential to thepractice of the invention.

Groupings of alternative elements or embodiments of the inventiondisclosed herein are not to be construed as limitations. Each groupmember can be referred to and claimed individually or in any combinationwith other members of the group or other elements found herein. One ormore members of a group can be included in, or deleted from a group forreasons of convenience and/or patentability. When any such inclusion ordeletion occurs, the specification is herein deemed to contain the groupas modified thus fulfilling the written description of all Markushgroups used in the appended claims.

As discussed herein, the energy consumption in a carbon dioxide captureprocess can be reduced using a solvent. In an embodiment, the energyconsumption of the carbon dioxide capture process can be reducedrelative to conventional chemical solvents and solvents through thespecific combination of AP and DMAMP.

The solvent can be used in a carbon dioxide capture system. In anembodiment, a carbon dioxide system can generally comprise an absorberfor contacting a lean solvent with a flue gas to absorb carbon dioxide.The rich solvent can then pass to a stripper where the carbon dioxidecan be released from the rich solvent to regenerate the lean solvent.

The solvent described herein can result in an absorption process havingreduced energy consumption. In general, there are three primarycontributors to the total energy consumption within a carbon dioxidecapture process. The first is the heat required to release CO₂ from therich solvent. This heat is supplied to reverse the carbon dioxideabsorption reaction with the chemical solvent and is strongly related tothe heat of absorption of carbon dioxide. A second contributor to thetotal energy consumption is heat loss by the system (for example, heatlosses due to finite temperature approaches in the cross exchanger,etc.). This can be reduced by proper system design. A third contributorto the total energy consumption is the heat of vaporization related tocreating steam in the stripper in order to strip carbon dioxide from therich solvent.

In an embodiment, the solvent used in the carbon dioxide capture systemor process can comprise AP, DMAMP, and water. DMAMP, being a stericallyhindered amine, is known to have low energy requirement for regenerationof the absorbent but the slow reaction kinetics have a negative impactin the absorber as it requires a longer contact time between the CO₂containing gas and the absorbent in the absorber. It is believed, andwithout being limited by theory, that the use of DMAMP in the solvent,in certain conditions and compositions disclosed herein, reduces thelikelihood that the solvent will precipitate a solid with CO₂, incontrast to other common compounds that may be used in the solvent.Therefore DMAMP may be combined with AP, which is known to have highenergy requirement.

According to the present embodiments, it is found that an aqueous CO₂absorbent comprising from approximately 5% to 55% by weight of DMAMP andfrom approximately 5% to 45% by weight of AP shows good reactionkinetics, absorption capacity, and low energy requirement. Additionally,utilizing the combination of DMAMP and AP results in an unexpecteddecrease in the energy consumption of the overall system and anunexpectedly high reaction rate.

The amount of the DMAMP utilized in the solvent can be expressed interms of a molar ratio relative to the amount of the AP utilized in thesolvent. In an embodiment, a molar ratio of the DMAMP to AP can be atleast about 0.05, at least about 0.1, or at least about 0.15. In anembodiment, a molar ratio of DMAMP to AP can be less than about 7.5,less than about 7.0, or less than about 6.5. In some embodiments, themolar ratio of DMAMP to AP can be in a range between any of the lowervalues to any of the upper values.

The balance of the solvent can include water. In some embodiments, thesolvent can comprise between about 1% and about 75% water. It should benoted that within a carbon dioxide system, the solvent can absorb waterfrom a flue gas, and therefore the amount of water at any point withinthe solvent in the system can vary. When discussed with respect to acarbon dioxide removal system, the solvent compositions described hereingenerally refer to the composition of the solvent in the lean solvent.For example, the solvent composition as described herein can be taken asthe solvent composition at or immediately upstream of the solvent feedto the absorber.

In an embodiment, the use of the solvent described herein can be used ina carbon dioxide absorption process. A process flowsheet of anembodiment of a CO₂ absorption system 100 is shown in FIG. 1. Exhaustgas (i.e. flue gas, carbonaceous gas, or gas containing CO₂) may begenerated by a combustion process of carbonaceous fuels and introducedthrough an exhaust pipe 1. The exhaust gas in the exhaust pipe 1 isintroduced into a direct contact cooler 2 where the exhaust gas iswashed and cooled by a countercurrent flow of water. The cooled exhaustgas is then introduced into an absorber 3. A lean solvent can passthrough lean absorbent pipe 4 into an upper portion of the absorber 3.The absorber 3 can comprise a distributor that evenly passes the solventover a packing or other internal structure (e.g., plates, trays, etc.)within the absorber to provide gas-liquid contact between the flue gasrising within the absorber 3 and the liquid solvent flowing down throughthe absorber 3. Within the absorber 3, the carbon dioxide within theexhaust gas can be absorbed within the solvent such that the amount ofcarbon dioxide within the solvent can increase as the solvent flows fromthe upper portion to the lower portion of the absorber 3.

The rich solvent containing the absorbed CO₂ can pass out of theabsorber 3 through rich solvent line 5. In addition to the carbondioxide, some amount of water from the water vapor in the flue gas canbe absorbed in the solvent within the absorber 3. The water canpartially dilute the solvent in the rich solvent stream. The CO₂ leanexhaust gas may be released into the surroundings through lean exhaustpipe 6 after being washed in a washing section by means of waterrecycled through washing water cooling circuits 19.

The rich absorbent in pipe 5 is heated against the lean absorbent inline 4 by means of a heat exchanger 7 before being introduced into astripper 8 (which may also be called a regeneration column) where therich absorbent is stripped by a countercurrent flow of steam. Thestripping steam is generated in a reboiler 11 in which lean absorbentcollected at the bottom of the stripper 8 is introduced through a leanabsorbent withdrawal pipe 10. Heat for steam production in the reboiler11 is added by means of steam introduced in steam pipe 13; the steam inpipe 13 is condensed in the reboiler 11 and is withdrawn throughcondensate pipe 13′.

Lean absorbent is withdrawn from the reboiler 11 in stream 10 andrecycled back into the stripper 8 in stream 12. Steam and CO₂ liberatedfrom the absorbent in the stripper 8 is washed in not shown washingsections by a countercurrent flow of water, before being withdrawnthrough CO₂ collection pipe 9. The CO₂ and steam is cooled in a cooler14, separated in a lean flash tank 15 to give water that is recycledinto the stripper 8 through a recycling line 17, and partly dried CO₂that is withdrawn through a pipe 16 for further treatment or use.

The process configuration illustrated in FIG. 1 includes severalelements that can result in energy savings, including when the solventdescribed herein is used with the system 100. The overall energyrequirements for the system 100 are based on the combined energy inputfor several components, principally the reboiler 11. The energyrequirements for the steam used in the reboiler 11 (i.e. reboiler duty)may be reduced based on the compounds used in the solvent. The reductionin the total system energy may be due to a number of effects includingan increased solubility of the carbon dioxide within the solventdescribed herein.

Overall, it is expected that the use of the solvent comprising AP andDMAMP can have a combined reduction in the total energy consumption whencompared to the use of a carbon dioxide removal system using a solventwith similar compounds at similar ratios.

For use in the solvent described above in FIG. 1, a solvent has beenidentified comprising water, AP, and DMAMP. This specific mixture ofcompounds exhibits properties that are unexpected, relative to theproperties of similar compounds or of pure DMAMP or pure AP. The use ofthis specific mixture of compounds in a solvent such as the onedescribed in FIG. 1 would result in an unexpected reduction in energyconsumption for the overall system 100.

As shown in the example of FIG. 2, vapor-liquid equilibrium, kinetic,and physical property data were developed for solvents composed of AP,DMAMP, water, and mixtures thereof. The data indicate that mixtures ofthe components yield a solvent with lower energy consumption than eitherpure component. In FIG. 2, the energy consumption (i.e. reboiler duty)is plotted against the solvent composition. From left to right on thex-axis, the AP concentration increases and the DMAMP concentrationdecreases. The molality of the solvent mixture is constant. The relativeenergy consumption is plotted on the y-axis. The relative energyconsumption is the reboiler duty divided by the CO₂ production rate,which is then normalized relative to the energy consumption of a pure APand water solution. The energy consumption may be affected by the CO₂loading of the rich and lean solvents (or delta loading).

One would have expected the energy consumption of a pure component to bethe lowest energy consumption and the energy consumption of mixtures tobe between the pure components. However this is not the case asimprovements in energy consumption are achieved unexpectedly by mixingAP with DMAMP in water. FIG. 2 shows that the energy consumption is aminimum at a specific mixture ratio. However, a decreased energyconsumption can be achieved when the solvent comprises betweenapproximately 5% AP and approximately 45% AP, and between approximately5% DMAMP and approximately 55% DMAMP, with the remainder of the solventcomprising water.

The components within the solvent may be at a number of ratios to oneanother to achieve this unexpected reduction in energy consumption. Theratio of AP to DMAMP within the solvent may be between 1:11 and 5:1. Asa first example, the ratio of AP to DMAMP within the solvent may beapproximately 1:10. As a second example, the ratio of AP to DMAMP withinthe solvent may be approximately 1:5. As a third example, the ratio ofAP to DMAMP within the solvent may be approximately 1:4. As a fourthexample, the ratio of AP to DMAMP within the solvent may beapproximately 1:2. As a fifth example, the ratio of AP to DMAMP withinthe solvent may be approximately 1:1. As a sixth example, the ratio ofAP to DMAMP within the solvent may be approximately 2:1. As a seventhexample, the ratio of AP to DMAMP within the solvent may beapproximately 3:1.

Another way of describing the components within the solvent may be as apercentage of the total solvent. For example, the AP within the solventmay be between 5 wt % and 45 wt % of the total solvent, and the DMAMPwithin the solvent may be between 5 wt % and 55 wt % of the totalsolvent. As a first example, the solvent may comprise approximately 5 wt% AP and approximately 55 wt % DMAMP. As a second example, the solventmay comprise approximately 10 wt % AP and approximately 45 wt % DMAMP.As a third example, the solvent may comprise approximately 12 wt % APand approximately 40 wt % DMAMP. As a fourth example, the solvent maycomprise approximately 20 wt % AP and approximately 35 wt % DMAMP. As afifth example, the solvent may comprise approximately 30 wt % AP andapproximately 30 wt % DMAMP. As a sixth example, the solvent maycomprise approximately 30 wt % AP and approximately 25 wt % DMAMP.

As shown in FIG. 2, the energy consumption decreases at leastapproximately 20% from the energy consumption at the pure components.“Pure” components may be defined as a solution containing only thatcomponent and water. In some embodiments, the energy consumptiondecreases approximately 25% from the energy consumption at the purecomponents. The energy consumption decreases at least betweenapproximately 0.6 GJ/t to approximately 1 GJ/t over the range of ratiosof the compounds. The reduction in energy consumption may be optimizedby selecting a specific ratio of AP and DMAMP. Additionally, thespecific combination of AP with DMAMP in the solvent results in thisunexpected decrease in energy consumption, where similar compounds atsimilar ratios do not result in a decrease in energy consumption.

In some embodiments of the system, the energy consumption of the systemwhen a solution containing AP, DMAMP, and water is used may decreasebetween approximately 10% and 35% from the energy consumption of thesystem when the solution contains only AP and water. In some embodimentsof the system, the energy consumption of the system when a solutioncontaining AP, DMAMP, and water is used may decrease betweenapproximately 20% and 30% from the energy consumption of the system whenthe solution contains only AP and water. In some embodiments of thesystem, the energy consumption of the system when a solution containingAP, DMAMP, and water is used may decrease approximately 25% from theenergy consumption of the system when the solution contains only AP andwater.

In some embodiments of the system, the energy consumption of the systemwhen a solution containing AP, DMAMP, and water is used may decreasebetween approximately 10% and 30% from the energy consumption of thesystem when the solution contains only DMAMP or AP, and water. In someembodiments of the system, the energy consumption of the system when asolution containing AP, DMAMP, and water is used may decrease betweenapproximately 15% and 25% from the energy consumption of the system whenthe solution contains only DMAMP and water. In some embodiments of thesystem, the energy consumption of the system when a solution containingAP, DMAMP, and water is used may decrease approximately 23% from theenergy consumption of the system when the solution contains only DMAMPand water.

Having described various systems and methods, various embodiments caninclude, but are not limited to:

In a first embodiment, a solvent for capture of carbon dioxide from agas mixture may comprise AP, in a concentration ranging from 5 wt % to45 wt %; DMAMP, where a mass ratio of DMAMP to AP is between about 1:11and 5:1; and water.

A second embodiment can include the solvent of the first embodiment,wherein the concentration of DMAMP is between approximately 10 wt % and55 wt %.

A third embodiment can include the solvent of the first or secondembodiments, wherein the concentration of AP is approximately 10 wt %and the concentration of DMAMP is approximately 45 wt %.

A fourth embodiment can include the solvent of any of the first to thirdembodiments, wherein the ratio of AP to DMAMP is approximately 1:10.

A fifth embodiment can include the solvent of any of the first to fourthembodiments, wherein the ratio of AP to DMAMP is approximately 1:5.

A sixth embodiment can include the solvent of any of the first to fifthembodiments, wherein the ratio of AP to DMAMP is approximately 1:2.

A seventh embodiment can include the solvent of any of the first tosixth embodiments, wherein the ratio of AP to DMAMP is approximately1:1.

An eighth embodiment can include the solvent of any of the first toseventh embodiments, wherein the ratio of AP to DMAMP is approximately3:1.

In a ninth embodiment, a method for capturing carbon dioxide from a gasmixture may comprise contacting a gaseous stream comprising carbondioxide with a lean solvent, wherein the lean solvent comprises AP,DMAMP, and water; absorbing at least a portion of the carbon dioxide inthe lean solvent to produce a rich solvent; transferring the richsolvent to a stripper, wherein the stripper comprises a reboiler;applying heat to the rich solvent using the reboiler; generating a vaporstream within the reboiler while incurring an energy consumption toregenerate the lean solvent, wherein the vapor stream comprises steamand at least a portion of the carbon dioxide from the rich solvent; andtransferring the vapor stream to a condenser.

A tenth embodiment can include the method of the ninth embodiment,wherein a heat duty of the condenser is reduced relative to acorresponding method in which the solvent does not include thecombination AP and DMAMP, and reducing the heat duty of the reboilerrelative to a corresponding process in which the solvent does notinclude the combination of AP and DMAMP.

An eleventh embodiment can include the method of the ninth or tenthembodiment, wherein the energy consumption of the method is reduced byat least 10% relative to a corresponding process in which the solventdoes not include the combination of AP and DMAMP.

A twelfth embodiment can include the method of any of the ninth toeleventh embodiments, wherein the lean solvent comprises a ratio of APto DMAMP between approximately 1:11 and 5:1.

A thirteenth embodiment can include the method of any of the ninth totwelfth embodiments, wherein the lean solvent comprises approximately 10wt % AP and approximately 40 wt % DMAMP.

A fourteenth embodiment can include the method of any of the ninth tothirteenth embodiments, wherein absorbing at least a portion of thecarbon dioxide in the lean solvent to produce a rich solvent does notform a precipitate.

A fifteenth embodiment can include the method of any of the ninth tofourteenth embodiments, further comprising generating a vapor stream byflashing the lean solvent from the reboiler in a lean flash tank;compressing the vapor stream from the lean flash tank; and reintroducingthe compressed vapor to the stripper.

In a sixteenth embodiment, a system for carbon dioxide capture from agas mixture may comprise a lean solvent comprising 3-amino-1-propanol(AP), 2-dimethylamino-2-methyl-1-propanol (DMAMP), and water; anabsorber containing at least a portion of the lean solvent, wherein theabsorber is configured to receive the lean solvent and a gaseous streamcomprising carbon dioxide, contact the lean solvent with the gaseousstream, and produce a rich solvent stream and a gaseous stream depletedin carbon dioxide; a stripper, wherein the stripper is configured toreceive the rich solvent stream; a cross-exchanger fluidly coupled to arich solvent outlet on the absorber and a rich solvent inlet on thestripper; a reboiler fluidly coupled to a lower portion of the stripper,wherein the reboiler is configured to generate a vapor stream from therich solvent and pass the vapor stream back to the stripper; and acondenser fluidly coupled to a vapor outlet of the stripper.

A seventeenth embodiment can include the system of the sixteenthembodiment, wherein the lean solvent comprises approximately 5 wt % to45 wt % AP and approximately 5 wt % and 55 wt % DMAMP.

An eighteenth embodiment can include the system of the sixteenth orseventeenth embodiments, wherein a ratio of DMAMP to AP in the leansolvent is between about 1:11 and about 5:1.

A nineteenth embodiment can include the system of any of the sixteenthto eighteenth embodiments, wherein the ratio of AP to DMAMP in the leansolvent is approximately 1:5.

A twentieth embodiment can include the system of any of the sixteenth tonineteenth embodiments, further comprising a flash tank fluidly coupledto the reboiler, wherein the flash tank is configured to receive anoutlet stream from the reboiler and generate the lean solvent stream anda vapor stream consisting mainly of steam; and a vapor compressorfluidly coupled to the flash tank, wherein the vapor compressor isconfigured to receive and compress the vapor stream and pass thecompressed vapor stream back to the stripper.

While various embodiments in accordance with the principles disclosedherein have been shown and described above, modifications thereof may bemade by one skilled in the art without departing from the spirit and theteachings of the disclosure. The embodiments described herein arerepresentative only and are not intended to be limiting. Manyvariations, combinations, and modifications are possible and are withinthe scope of the disclosure. Alternative embodiments that result fromcombining, integrating, and/or omitting features of the embodiment(s)are also within the scope of the disclosure. Accordingly, the scope ofprotection is not limited by the description set out above, but isdefined by the claims which follow that scope including all equivalentsof the subject matter of the claims. Each and every claim isincorporated as further disclosure into the specification, and theclaims are embodiment(s) of the present invention(s). Furthermore, anyadvantages and features described above may relate to specificembodiments, but shall not limit the application of such issued claimsto processes and structures accomplishing any or all of the aboveadvantages or having any or all of the above features.

Additionally, the section headings used herein are provided forconsistency with the suggestions under 37 C.F.R. 1.77 or to otherwiseprovide organizational cues. These headings shall not limit orcharacterize the invention(s) set out in any claims that may issue fromthis disclosure. Specifically and by way of example, although theheadings might refer to a “Field,” the claims should not be limited bythe language chosen under this heading to describe the so-called field.Further, a description of a technology in the “Background” is not to beconstrued as an admission that certain technology is prior art to anyinvention(s) in this disclosure. Neither is the “Summary” to beconsidered as a limiting characterization of the invention(s) set forthin issued claims. Furthermore, any reference in this disclosure to“invention” in the singular should not be used to argue that there isonly a single point of novelty in this disclosure. Multiple inventionsmay be set forth according to the limitations of the multiple claimsissuing from this disclosure, and such claims accordingly define theinvention(s), and their equivalents, that are protected thereby. In allinstances, the scope of the claims shall be considered on their ownmerits in light of this disclosure, but should not be constrained by theheadings set forth herein.

Use of broader terms such as “comprises,” “includes,” and “having”should be understood to provide support for narrower terms such as“consisting of,” “consisting essentially of,” and “comprisedsubstantially of.” Use of the terms “optionally,” “may,” “might,”“possibly,” and the like with respect to any element of an embodimentmeans that the element is not required, or alternatively, the element isrequired, both alternatives being within the scope of the embodiment(s).Also, references to examples are merely provided for illustrativepurposes, and are not intended to be exclusive.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods may beembodied in many other specific forms without departing from the spiritor scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted or not implemented.

Also, techniques, systems, subsystems, and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as directly coupled or communicating witheach other may be indirectly coupled or communicating through someinterface, device, or intermediate component, whether electrically,mechanically, or otherwise. Other examples of changes, substitutions,and alterations are ascertainable by one skilled in the art and could bemade without departing from the spirit and scope disclosed herein.

What is claimed is:
 1. A method for capturing carbon dioxide from a gasmixture comprising: contacting a gaseous stream comprising carbondioxide with a lean solvent, wherein the lean solvent comprises3-amino-1-propanol (AP), 2-dimethylamino-2-methyl-1-propanol (DMAMP),and water; absorbing at least a portion of the carbon dioxide in thelean solvent to produce a rich solvent; transferring the rich solvent toa stripper, wherein the stripper comprises a reboiler; applying heat tothe rich solvent using the reboiler; generating a vapor stream withinthe reboiler while incurring an energy consumption to regenerate thelean solvent, wherein the vapor stream comprises steam and at least aportion of the carbon dioxide from the rich solvent; and transferringthe vapor stream to a condenser.
 2. The method of claim 1, wherein aheat duty of the condenser is reduced relative to a corresponding methodin which the solvent does not include the combination AP and DMAMP, andreducing a heat duty of the reboiler relative to a corresponding processin which the solvent does not include the combination of AP and DMAMP.3. The method of claim 1, wherein the energy consumption of the methodis reduced by at least 5% relative to a corresponding process in whichthe solvent does not include the combination of AP and DMAMP.
 4. Themethod of claim 1, wherein the lean solvent comprises a ratio of AP toDMAMP between approximately 1:11 and 5:1.
 5. The method of claim 1,wherein the lean solvent comprises approximately 10 wt % AP andapproximately 40 wt % DMAMP.
 6. The method of claim 5, wherein absorbingat least a portion of the carbon dioxide in the lean solvent to producea rich solvent does not form a precipitate.
 7. The method of claim 1,further comprising: generating a vapor stream by flashing the leansolvent from the reboiler in a lean flash tank; compressing the vaporstream from the lean flash tank; and reintroducing the compressed vaporto the stripper.